For example, in a fan that blows out air, an impeller which has blades (vanes) and rotates around a rotation axis to generate a flow of air, is a significant part that greatly influences performance. When the center of gravity of the impeller is shifted (mass eccentricity) (the center of gravity is in a position other than the rotation axis), rotation of the impeller causes a large vibration. Hence, users feel discomfort from the vibration of the impeller, noise from the vibration, and the like.
Against this background, a technique has been proposed (see Patent Literature 1, for example), in which a balance weight (a weight) is attached to an impeller so that the position of the center of gravity of the impeller coincides with the rotation axis. Since the position of the center of gravity often differs among impellers, the balance weight is attached to a corresponding position according to each of the impellers.